This proposal addresses the functions of the dorsolateral prefrontal cortex at two levels of inquiry: at the systems level, experiments will examine the cognitive and vasomotor functions of the prefrontal cortex by specifying the processes embodied in delay related neuronal activity which occurs during memorization of an item of information; at the cellular level, experiments examine the local circuit interactions between pyramidal cells and interneurons that underlie these functions. Project 1 addresses the basis of the stimulus selectivity of the interior convexity of the dorsolateral prefrontal cortex. Two possible explanations will be tested. One, that stimulus selectivity is due to sensory factors such as preference for color or shape. Two, that inferior convexity neuronal activity reflects cognitive mechanisms related to stimulus categorization. Experiments will employ different classes of stimuli (color swatches, geometric shapes, as well as faces and other meaningful stimuli) to assess the basis of stimulus selectivity. Project 1 focuses on possible functions of delay-related neuronal activity in memory tasks. A distinction is made between the processes of recall and rehearsal as candidate functions and two different memory tasks have been designed to dissociate these alternatives. The experiments also examine the possibility that the magnitude of delay activity is related to the tuning of neurons to a sensory dimension. Project 3 will record from pairs of putative GABAergic interneurons (fast-spiking cells and pyramidal cells (regular-spiking neurons) in order to clarify the role of the GABAergic system in the prefrontal cortex. Experiments are designed to test predictions about the behavior of fast and regular-spiking neurons on the hypothesis that fast-spiking cells are interneurons. Experiments will examine the similarities and differences between interneurons and pyramidal cell pairs that are located within a vertical "column" by simultaneous recordings. Data for these experiments will be obtained during the vasomotor and memory tasks of Projects 1 and 2, and will provide insight on the role of GABAergic mechanisms during cognitive behaviors. These experiments will shed light on the normal operation of cognitive mechanisms of the prefrontal cortex and their local neural basis. These data are relevant to disorders such as schizophrenia which appear to reflect the dysfunction of the frontal lobes.